The present invention relates to an ocular lens and a process for its production, particularly to an ocular lens having a surface layer constituted by a component different from a polymerizable component of the main body of the ocular lens, and a process for its production.
As a method to correct a sight, lenses are widely used. As ocular lenses, there are not only those that are put on the eyeballs such as contact lenses, but also so called intraocular lenses, which are inserted in the eyeballs of cataract patients after extracting crystalline lenses.
Heretofore, these ocular lenses used to be produced by a cutting process. However, because of a problem in productivity, the process has been changed to a mold-polymerization using a mold. In the process of mold-polymerization, the mold is constituted by a combination of a male mold and a female mold, and a lens material is filled and polymerized in a space formed between them to obtain an ocular lens stock material. The obtained ocular lens stock material is released from the mold and subjected to a treatment such as removing unreacted residual components, to obtain an ocular lens.
In recent years, as a cause of ocular disease of ocular lens wearers, attention has been drawn to lowering of the hydrophilic property (the tear wettability), or adhesion of contaminants such as proteins or fats on the surface of the ocular lens. Therefore, in order to prevent ocular disease, improvements of an ocular lens with regard to the hydrophilic property of the ocular lens surface and preventing the adhesion of contaminants on its surface, have been sought.
For example, JP-A-57-34518 discloses a method for improving the water wettability by subjecting the surface of an ocular lens stock material to plasma treatment to modify it. Further, JP-A-6-49251 discloses a method of grafting a hydrophilic monomer to the surface of an ocular lens stock material, also to modify the surface of the ocular lens.
However, by these methods, the surface of the ocular lens stock material once formed is subjected to the physical-chemical treatment, whereby deformation is induced to the ocular lens stock material, and consequently the necessary shape can not be obtained when the ocular lens is completed.
On the other hand, PCT International Publication WO00/04078 discloses a process which comprises coating the mold surface with a solution of a polymer having dipolar ion groups excellent in biocompatibility, and producing a lens polymer by using the coated mold, to obtain an ocular lens stock material having a polymer coating layer on its surface. This process can form the entire ocular lens stock material including the coating layer on the surface by a single step of polymerization, whereby as compared with the above-mentioned process of subjecting the lens stock material after polymerization to a treatment, it is considered to be superior in that deformation of the lens stock material can be avoided.
However, this method has a problem that when the mold is coated with the polymer solution, the solution tends to pool along the shape of the mold, whereby the coating layer will be formed nonuniformly. Usually, the coating layer is constituted by a material different from the polymerizable component of the ocular lens, and accordingly nonuniform formation of the coating layer tends to lead to deformation of the ocular lens material or cloudiness when it is polymerized, and potentially jeopardizes optical functions of the ocular lens.
Accordingly, an object of the present invention is to provide an ocular lens without accompanying deformation induced in the process, and having a uniform coating layer on its surface. Another object is to produce an ocular lens stock material having a uniform coating layer on its surface by a single step of mold-polymerization.
The ocular lens of the present invention is produced by a process comprising a step of irradiating with an excimer light at least a part of molding surface of the mold for shaping an ocular lens surface, a step of uniformly coating the mold surface irradiated with the excimer light, with a compound or a solution of such compound which will form a coating layer, a step of filling an ocular lens material into the mold and polymerizing it, a step of releasing a polymer obtained by the polymerization from the mold, to obtain an ocular lens stock material having the above-mentioned compound fixed on its surface, and a step of extracting an unfixed and unreacted compound from the obtained ocular lens stock material.
The compound to form a coating layer is a compound fixable to the surface of the ocular lens by an interaction with a polymerizable component in the ocular lens material.